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in order to promote transparency and accountability in the working of every public authority, 
and whereas the attached publication of the Bureau of Indian Standards is of particular interest 
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Mazdoor Kisan Shakti Sangathan 
"The Right to Information, The Right to Live'' 

IS 5182 (Part 10) (1999, Reaffirmed 2009) : Methods for 
Measurement of Air Pollution, Part 10: Carbon Monoxide 
(First Revision). ICS 13.040.20 : 17.060 

Jawaharlal Nehru 
'Step Out From the Old to the New" 

aj^&vi iJii^s:y%K^ isb^^ni^seg 

:<>5&i| mT'5K^5?::5:^>^i»l 


Satyanarayan Gangaram Pitroda 
Invent a New India Using Knowledge 

Bhartrhari — Nitisatakam 
''Knowledge is such a treasure which cannot be stolen" 



(Reaffirmed 2009) 

IS 5182 (Part 10): 1999 

( Reaffirmed 2003 ) 

Indian Standard 


( First Revision ) 

ICS 13.040.20;17.060 

©BIS 1999 


NEW DELHI 110002 

Oaober 1999 Price Gpjup 4 

Air Environmental Protection Sectional Committee, CHD 032 


This Indian Standard (First Revision) was adopted by the Bureau of Indian Standards after the draft finalized 
by flie Air Environmental Protection Sectional Committee had been approved by the Chemical Division Council. 

Devices and techniques for determining the concentration of pollutants in the atmosphere are important for the 
assessment of ambient air quality, establishing hazardous levels in the environment, determining the effectiveness 
of ameliorating measures and appraisal of contamination from a process or source. Carbon monoxide is of interest 
as an air contaminant because of its known toxic properties. It is produced mainly from the incomplete combustion 
of carbonaceous fuels. The exhaust gases from motor vehicles constitute a large source of carbon monoxide in 
an urban area. Other sources are the combustion products of fuels used for power, steam and heating purposes. 

Carbon monoxide is not known to participate in secondary atmospheric reactions. Its primary effect on human 
health is dependent on its great affinity for hemoglobin, the oxygen transporting pigment of the blood. Carbon 
monoxide tends to combine with hemoglobin 210 times as readily as does oxygen, thus effectively preventing its 
important function of transporting the oxygen from the lungs to the tissues. However, the combination of carbon 
monoxide with hemoglobin is spontaneously but slowly reversible, and the blood tends to be cleared of carbon 
monoxide in exponential fashion with a half time of 3 to 4 hours. 

Carbon monoxide occurs in unpolluted urban atmospheres in low concentrations, usually in the range of less 
than 1 part per million of air by volume. The first symptoms of carbon monoxide intoxication are headache, 
dizziness and lassitude. In most of the persons symptoms are first observed at carbon monoxide concentrations 
of about 100 mg/1, provided the exposure is sufficiently prolonged. It has been estimated that for each 1 mg/1 of 
carbon monoxide with which the human body is in equiltbriimi, 0. 16 percent of the body's hemoglobin will be 
inactivated by the formation of carboxy-hemoglobin. 

Carbon monoxide is so common a pollutant that exposure to it occurs in many occupations, like garage workers, 
traffic policemen, railway engine and yard staff Cigarette smoke also contams a considerable amount of carbon 
monoxide. Although adaptation to long term low level carbon monoxide exposure occurs, it seems likely that the 
addition of 5 percent of carboxy-hemoglobin by community air pollution to that caused by these other exposures 
may be sufficient to pose a substantial risk to the health of sensitive persons. Such a level might be produced by 
exposure of 30 mgA, of the carbon monoxide in polluted air for 4 to 6 hours or exposure to 120 mg/1 for one hour, 
A number of methods are available for the analysis of carbon monoxide. Larger proportions of carbon monoxide 
are usually determined by volumetric gas analysis, carbon monoxide being either oxidized to carbon dioxide with 
hot copper oxide or absorbed in a reagent containing cuprous salts. Small amounts of carbon monoxide are 
determined by some colorimetric reaction or by oxidizing to carbon dioxide and determination of either carbon 
dioxide or one of the other products of the reaction. In air pollution studies the normal range of carbon monoxide 
concentration would fall between 1 to 100 mg/l. Consequently, methods for the detection of short averages and 
maximum concoitrations of carbcm monoxide in the ambient air must be sensitive and accurate in the microchemical 
range. Other desirable features for a method should include a high degree of specificity, ease of operation and 
calibration and minimum interference from the other contaminants present in the air sample. 

Oxidation with iodine pentoxide and colour reaction with palladous salts and ammonium molybdate are most 
commonly used methods for the determination of carbon monoxide in polluted air samples. The iodine pentoxide 
method developed by American Gas Association Laboratory is an accurate and convenient method. Besides, 
non-dispersive infrared absorption method and gas chromatography method are also gaining important because 
of ease of operation, accuracy of test results, etc. 

The indicator tube method developed by the National Bureau of Standards, USA, is based upon a colour reaction 
with palladous salt and ammonium molybdate. Highly purified silica gel impregnated with anmionium molybdate 
and a solution of palladium or palladium oxide digested in sulphuric acid forming palladium silicomolybdate is 
exposed to carbon monoxide. A mofybdate blue is formed, the depth of colour in the detector tube varying from 
faint green to blue in proportion to the amount of carbon monoxide present in the air being tested. The indicator 
tubes being available now commercially, the carbon monoxide can be detemiined quickly and accurately. 

(Continued on third cover) 

!S 5182 (Part 10) : 1999 

Indian Standard 


( First Revision ) 


i . I This standard describes the details of the following 
live methods for the measurement of carbon monoxide 
in air: 

a) Iodine Pentoxide Method; 

b) Indicator Tube Method; 

c) Non-dispersive Infrared Absorption Method; 

d) Gas Chromatography Method; and 

e) Catalytic Oxidation Method. 

1.2 The indicator tube method is recommended for 
routine use. 

The iodine pentoxide method, non-dispersive infrared 
absorption method, gas chromatography method and 
catalytic oxidation method are recommended for use 
as reference methods where laboratory facilities are 


2.1 Principle 

The basis of this method is the following reaction 
between carbon monoxide and iodine pentoxide within 
135''C to ISO^'C to yield carbon dioxide and iodine 


The concentration of carbon monoxide in the air sample 
may be determined by analysis of the amount of either 
carbon dioxide or iodine produced. The air sample 
should be free from any iodine vapours or carbon 
dioxide. Substances, such as water vapour, unsaturated 
hydrocarbons, aldehydes and other organic 
compounds which may react with the iodine pentoxide 
or the liberated iodine could cause interference. It is, 
therefore, necessary to pass the air sample through an 
elaborate purification train consisting of activated 
carbon, an efficient drying agent, a chromic acid wash 
tower and some solid absorbent to remove carbon 

The dry air is then passed through a U-tube containing 
iodine pentoxide. Free iodine is liberated according to 
the above reaction if carbon monoxide is present. The 
iodine liberated in the reaction is absorbed in potassium 
iodide solution and titrated with standard sodium 

thiosulphate solution. 

2.2 Apparatus 

The apparatus may be easily fabricated {see Fig. I ). It 
consists of a chromic acid scrubber, a drying tube 
containing phosphorus pentoxide and potassium 
hydroxide, a U-tube packed with iodine pentoxide 
maintained at correct temperature ( 1 45''C), and bubbler 
to absorb either carbon dioxide in baryta or iodine in 
potassium iodide solution or a known volume of 
standard thiosulphate solution. 

2.3 Reagents 

2.3. 1 Iodine Pentoxide 

Analytical grade iodine pentoxide shall be used. One 
tube may need about 1 50 g. 

2.3.2 Chromic Acid 

Dissolve 70 g of finely ground potassium dichromate 
in I 000 ml of concentrated sulphuric acid while heating 
cautiously under a hood; cool and decant. Permit this 
solution to stand and then decant the supernatant 


2.3.3 Potassium Iodide Solution 

This shall be prepared fresh before an analysis has to 
be done. Dissolve about 10 g of potassium iodide in 
100 ml of water. The reagent shall be stored in a dark 
coloured bottle. Test the reagent for the presence of 
free iodine by use of starch and reject if the solution 
gives a positive test. 

2.3.4 Starch Indicator Solution 

Fresh solution shall be prepared. Suspend 2 or 3 g of 
starch in a few millilitres of water and make a paste. 
Add this to 200 ml of water, heat just to boiling and 
cool to room temperature. 

2.3.5 Sodium Thiosulphate Solution - 0.001 N. 

Weigh out 24.8 g of reagent grade sodium thiosulphate 
and 2 to 3 g of borax crystals. Dissolve this in I litre of 
water. This is an approximately 0.1 N solution. Taking 
10 ml of this solution and diluting it to I litre would 
give approximately 0.00 1 N solution. Standardize either 
with potassium dichromate solution or with iodine 
solution at least once a week. 

IS 5182 (Part 10) : 1999 

A - Sampling burette (500 ml) 

6 - Water jacket 

C - Chromic acid wash tower containing chromic acid and glass beads 

D - Drying tube: The / - tube contains alternate layers of phosphorus pentoxide and glass wool with a layer 

of potassium hydroxide pellets at the Inlet side of g . It Is sealed with paraffin wax 
E - Iodine pentoxide tube having alternate layers (about 15 mm) of iodine pentoxide and glass wool 
F - Furnace 
G - Potassium iodine trap 
Stopcocks « S,. Sj. S3 and S^ 
Rubber tubye joints - L,, L^ and L^ 
Standard joints - Jy J^ and J3 

Fig. 1 Apparatus for Determination of Carbon Monoxide Sodium thiosulphate solution is not stable, 
and is affected by oxygen, carbon dioxide and micro- 
organisms. For this reason it is essential to use boiled 
water in its preparation and to include a preservative 
like borax, 

2.3-5.2 Standardization of thiosulphate solution 

a) With potassium dichromate 

Dissolve 0.5 g of potassium iodide and ! g of 
sodium bicarbonate in 30 ml of water in 125 ml 
glass stoppered long necked flask. Then add 
concentrated hydrochloric acid slowly, swirling the 
flask, until no more carbon dioxide is generated 
and add about 1 ml more of acid. Mow add 20 ml of 
0.00 1 N potassium dichromate solution. Swirl the 
mixture very gently. Wash the sides of the flask 
with a few millilitres of water and allow this rinse to 

form a layer above the acid dichromate solution 
without m ixing. Stopper the flask and allow to stand 
for about 10 minutes in dark. Mix thoroughly, 
remove the stopper and run in the 0.001 N sodium 
thiosulphate solultion to be standardized from a 
volumetric burette until the solution becomes light 
yellow. Add a few drops of starch indicator solution 
and continue the titration until the bright blue 
colour has disappeared and only the pale green 
colour of the chromic chloride remains. Add the 
last few drops very cautiously. Calculate the 
normality of the sodium thiosulphate solution. 

b) With Iodine 

Place 10 ml of standard 0.001 N iodine solution in a 
125-ml long necked flask. Titrate with 0,001 N 
sodium thiosulphate solution to be standardized 
until yellow colour of the iodine solution is very 

IS 5182 (Part 10) : 1999 

faint. Add a few drops of starch indicator solution, 
mix by swirling, and continue the titration adding 
the sodilim thiosulphate solution drop by drop 
until the blue colour is discharged. Calculate the 
normality of the sodium thiosulphate solution. 

2.4 Procedure 

2.4.1 The iodine pentoxide tube shall be thoroughly 
purged from free iodine. This is accomplished by 
heating the tube to 200^C and passing nitrogen gas 
through stopcock S^ till no colour change is observed 
on adding starch indicator to the potassium iodide 
solution in the trap. This may take as long as 5 days. 
Stopcocks S^ and 5^^ should then be greased and kept 
closed to avoid exposing the iodine pentoxide tube to 
moisture from the air. 

2.4.2 A blank determination shall be made before any 
analysis is to be performed. Fresh 10 percent potassium 
iodide solution is taken in the trap. Nitrogen is passed 
through stopcock S^ for 30 minutes, keeping stopcocks 
S^ and S^ open. Stopcocks S^ and S^ are now closed 
and the solution in the potassium iodide trap titrated 
with standard sodium thiosulphate solution. The 
amount of free iodine thus obtained is considered the 
blank of the apparatus and should be subtracted from 
subsequent determinations. 

2.4.3 Known volume of the air sample is taken in the 
sample burette. A through stopcock S^ and allowed to 
stand until it attains the temperature of the water in the 
jacket B. Potassium iodide trap is filled with potassium 
iodide solution and attached to the apparatus. 
Stopcocks iS,i 5^, S^ and S^ are opened so that the gas 
burette is connected to the iodine pentoxide tube. The 
gas is then slowly pushed by raising the water level in 
the gas burette A. This takes approximately 7 to 10 
minutes. When all the gas has been passed,. stopcocks 
5, and S^ are closed. The apparatus is again purged 
with nitrogen for about 30 minutes. Stopcocks S^ and 
S^ are closed. The potassium iodide trap is 
disconnected and its contents titrated for free iodine. 

2.4.4 In case the concentration of carbon monoxide in 
the test sample exceeds O.l percent, only a small 
portion of the sample should be passed through the 
apparatus at a time in order to avoid the release of 
excessive amounts of free iodine, which may deposit 
in the form of crystals and cause choking. As the 
carbon monoxide concentration in atmospheric 
po llution normally falls much below this level, it is usual 
practice to pass the entire volume of the gas sample 
through the apparatus. 

2.5 Catculation 

2.5. 1 If carbon monoxide is present in the sample being 
analysed, then iodine is evolved and titrated in 
accordance with the following equations; 

1,0, + 5 CO = 1, + 5CO2 

l, + 2Ma2Sp3=2NaI + Na2S,0, 

Expressed numerically on mass basis: 

140gCO - 253.8g Ij = 496.4gNa2Sj03 5Hp 

Since a normal solution of iodine contains 0.127 g of 
iodine per millilitre, then according to the above 
equations the equivalent mass of sodium thiosulphate 
and carbon monoxide is 0.248 g and 0.07 g respectively. 

Now volume of 0.07 g of carbon monoxide at standard 
temperature and pressure (STP) (O^C and 760 mm Hg) 
is given by: 

22 400 X 0.07 

= 56ml 

Hence, 1 ml of normal sodium thiosulphate solution, 
containing 0.248 g is equivalent to 0.07 g or 56 ml of 
carbon monoxide. 

Therefore, volume of carbon monoxide in the sample 
analyzed is given by: 

56 X Volume of thiosulphate in ml X normality of 
thiosulphate (where the volume of sodium thiosulphate 
used in ml is the volume to titrate the iodine liberated in 
the analysis of the sample). 

Carbon monoxide, (ig/m^ 

0.07 X Volume of thiosulphate x 
Nomiality of thiosulphate x 10^ 

Volume of 
gas sampled (litre) 


3.1 Principle 

Carbon monoxide reduces yellow silicomolybdate 
to lower oxides. The colour changes from yellowish 
green to green and finally deep blue depending on the 
extent of reduction which again under identical 
conditions depends on concentration of carbon 
monoxide in air. 

3.2 Interferences 

Hydrogen sulphide, unsaturated hydrocarbons, 
moisture, etc, interfere but they may be removed by 
passing the sample through various absorbents 
provided with the indicator tubes. 

3.3 Procedure 

Follow the manufacturer's instructions carefully. Draw 
250 ml of die sample at the prescribed rate (40 to 50 ml/ 
min) through the tube by the aspirator provided. 
Compare the colour produced with the standard colours 
provided and calculate the concentrations. 

IS 5182 (Part 10) : 1999 


4.1 Principle 

Samples containing carbon monoxide in the range of 
to 1 00 mg/l are analyzed on a non-dispersive infrared 
absorption gas analyser, namely, an electro-optical 
spectrophotometer with no spectra! dispersion 
component. It may consist of a single or double source 
of infrared energy and one or more infrared detectors 
separated by an optical cell or cells through one or 
more of which the sample flows, whereby the specific 
spectral absorption of the component of interest is 


! Specific spectral sensitivity is obtained by either a selective 
source or a selective detector and may be improved further by 
tllters in the light path. 

2 The analyser shall be constructed to or be adjusted to select 
only the spectral bands at which carbon monoxide has its 
characteristic absorption, and the sample cell length shall be 
appropriate for the rated range of concentration. 

3 Though the basic instrument recommended is for (0 to 100) 
mg/l range, for samples of higher mg/I range the instrument 
may be used with proper dilution and conditioning of the 
samples. The dilution shall meet all other conditions given 
in 4.3 

4.2 Apparatus 

4.2.1 Infrared Gas A nalyser 

Any non-dispersive type, provided it meets the 
following requirements: 

a) The apparatus shall be constructed so as to be 
suitable for operating within the temperature range 
of 1 S^C to 40*^0 and in a relative humidity range of 
to 90 percent. The apparatus shall embody 
facilities for the analysis of continuously applied 
sample or a discrete sample of volume of 2.0 litres. 
In the later case the purification train shall be of 
such a design and dead volume that 2.0 litres is 
adequate for its proper flushing out. The apparatus 
shall include facilities for the visual inspection of 
results and also for their recording. The scale shall 
he divided Into steps of l.O percent full scale 
division (fsd). 

b) The 95-percent confidence limits of the repeata- 
bility shall be within ± 1 .0 percent full scale division 
(fsd). The minimum detectable concentration shall 
be 1 mg/l or less; 

c) The cross sensitivities (or interference) of the 
analyser to carbon dioxide and to water vapour 
shall each be less than I percent full scale division 


d) The maximum deviation between an actual 
instrument reading and the reading predicted 

by a straight line between the upper and lower 
calibration points shall be 1 percent full scale 
division (fsd); 

e) Neither the zero drift nor the full scale drift shall 
be greater than ± 1 percent fsd in 24 hours, 
excluding change due to changes of atmos- 
pheric pressure; 

i) The response time of the analyser excluding the 
sample conditioning train shall be less than 40 sec 
to 90 percent of the final reading at a flow rate of 

g) The apparatus shall be capable of meeting the 
requirements in 4.2.1(a) to 4.2.1(f) despite a 
variation of ± 10 percent in the nominal applied 
mains voltage. The requirement may be met by 
incorporating a voltage stabilizer either within the 
instrument or externally. 

4.2.2 Pump 

4.2.3 Flowmeter 

4.2.4 Connecting Tubes 

Stainless steel, teflon, polyvinyl chloride or 

4.2.5 Arrangement of Apparatus 

The analysing system consists of two major parts, 
namely, the sample conditioning train and the infrared 
gas analyser itself. 

A pump is necessary to move the sample through the 
conditioning train and through the analyser. The pump 
may be sited before or after the analyser unit: 

a) Pump after the analyser (suction system) — If the 
pump is installed after the analyser, false readings 
and damage to the instrument by acci- 
dental overpressurizing are completely obviated. 
However, leak at any point may give rise to an 

b) Pump before the analyser (pressure system)— 
Minor leaks in the system do not invalidate the 
results of the analysis. The pump shall be of a 
type that will not contaminate the samples, 
Neoprene diaphragm and stainless steel below 
pumps have been found suitable. 

In both cases it may be necessary to install a reducing 
valve between the pump and the analyser in order to 
prevent pressure pulses by the pump influencing the 

A flowmeter shall also be incorporated in the sample 
flow line, preferably before the analyser. 

Connecting tubing will be required between the filter, 
pump, instrument, etc, as well as for the construction 

of the sampling probe. Stainless steel, teflon, PVC 
and polyethylene have been found suitable for this 

It is to be noted that the length of connecting tube may 
have to be kept to a minimum in order that the apparatus 
meets the performance requirements of 4.2.1 

4.3 Sample Conditioning 

4-3. 1 Particulate Matter 

Fine particulate matter causes scattering of the infrared 
beam, producing a positive interference and although 
small amounts may not affect the immediate reading 
they are objectionable because dust may accumulate 
on the optics of the instrument leading to reduced 
sensitivity and permanent impairment. To obviate these 
difficulties a filter capable of removing 99 percent of all 
particulate matter above 1 .0 \xm is essential and these 
should be installed immediately prior to the analysis 
cell. The filters may be wanned to prevent condensation 
occurring within them. Filters with elements made of 
fibre glass or sintered metal are suitable. These filters 
should be cleaned or changed periodically in order to 
avoid building up pressure acroiss the filtering 
membrane and thus affecting the flow of gas through 
the analysis cell. 

To minimize the frequency of changing the filter it is 
normally advisable to incorporate a preliminary coarse 
filter for which a porosity of 10 jim is suitable and 
this may be placed ^t the entrance to the sample 
conditioning train. 

4.3.2 Water Vapour 

Most ambient atmospheres contain sufficient water 
vapour to produce interference and the diurnal pattern 
of atmospheric humidity change may lead to variations 
in the degree of interference from hour to hour and day 
to day. 

There are three methods for eliminating the interference 
by water vapour: 

a) Humidification 

Saturation of the sample to constant humidity is 
applicable in all cases but for adequate 
repeatability the temperature of the saturator shall 
be kept within ±0.rC. 

NOTE — There may be long term deterioration of the 
optics of some instruments when continuously exposed 
to saturated sample streams. 

b) Refrigeration 

Refrigeration of the sample steam is always 
applicable but attention is drawn to the increase 
in dead volume of the apparatus which the 
refrigerated tubes entail. Conformity to the 
response time shall be confirmed experimentally. 

IS 5182 (Part 10) : 1999 

A final column of self-indicating desiccant shall 
be put at the end of the purifying train to give 
warning of a failure of the refrigerator. 

c) Desiccants 

The use of drying agents is always permissible, 
but to achieve adequate desiccation capacity 
between servicing intervals low rates of flow and 
large containers have to be used. These do not 
only make substantial additions to the response 
time but also allow a degree of mixing and hence 
loss in sharpness in response to steep changes 
of concentration. 

Desiccants tend to swell as they absorb water 
giving rise to increasing obstruction to the sample 

Desiccant towers and saturation vessels are 
typically constructed of glass and suitable 
desiccants include self-indicating magnesium 

4.3*3 Carbon Dioxide 

Optical filters are adequate for eliminating interference 
due to carbon dioxide up to 2 percent. 

Samples that may contain more than this will require 
purification, for example, by the use of soda lime. In 
this case, the difficulties that arise from the use of 
drying towers for the removal of water vapour also 
occur and the precautions recommended in that case 
also taken. 

4.3.4 Response Time 

The response time of the analyser and the conditioning 
train together shall be 2 minutes to reach 90 percent of 
the final reading. 

4.3.5 Changes due to Conditioning 

For accurate analysis, it may be important to calculate 
the change in concentration brought about by the 
process of purifying the sample. 

4.4 Mode of Operation 

4A1 Continuous Analysis 

Infrared analysers are normally used for continuous 
analysis and for this purpose fiow rate between 1 00 ml 
per minute to 1 000 ml per minute are suitable. 

4.4.2 Discrete Samples 

When used to analyse discrete samples the whole 
system shall be thoroughly flushed with the sample 
before each analysis and the whole system shall 
therefore be of such a volume and design that 1 000 ml 
is adequate for this purpose. 

IS 5182 (Part 10) : 1999 

4.5 Procedure 

4.5.1 Warm-Up Period 

Infrared analysers are normally operated on a 
continuous basis; however, an initial warm-up period 
is required and no readings shall be taken until the 
apparatus has reached steady temperature conditions 
and is giving a steady response. This shall not be 
more than 6 h. 

When used to analyse discrete samples, similar 
precautions to ensure that the apparatus has reached 
temperature stability shall also be taken. 

4.5.2 Calculation of Results 

Infrared analysers are calibrated variously in arbitrary 
units, in microvolts or in units of concentration and no 
one method of calculating results can be given. Infrared 
analysers which are not calibrated in units of 
concentration shall be accompanied with a precise 
statement of how a scale reading is to be converted to 
concentration of carbon monoxide. 

4.6 Standardization 

4.6. 1 Preparation of Standard Gases 

Infrared methods of gas analysis depend on calibration 
against gas mixtures of known composition. Method 
of preparing reference mixtures of standard gases shall 
be in accordance with the relevant Indian Standard. In 
the absence of these, they shall be prepared as agreed 
to between parties concerned. 

4.6.2 Calibration Gases 

Two standard gas mixtures are required for calibration 
purposes. One shall contain between 90 to 100 mg/l of 
carbon monoxide in air or nitrogen (span gas) and the 
other air or nitrogen with not more than I mg/l carbon 
monoxide (zero gas), 

4.6.3 Analysis of Standard Gases 

The span and zero gases shall be supplied to the 
instrument for calibration at the same temperature, 
humidity and pressure as will obtain when samples are 
to be analysed. Calibration mixtures shall be passed 
through the sample conditioning train. 


5.1 Principle 

A sample of the air containing carbon monoxide is 
injected into the gas chromatograph where it is carried 
from one end of the column to the other. During its 
movement, the constituents of the sample undergo 
distribution at -different rates and ultimately 
get separated. The separated constituents emerge from 
the end of the column one after the other and are 

detected by suitable means whose response is related 
to the amount of a specific component leaving the 

NOTE — The lower detection fimil of this method is 10 mg/l 
and sample size is 10 ml. 

5.2 Apparatus 

5.2J Any gas chromatograph capable of being 
operated under conditions given below for resolving 
the sample into distinct peaks may be used. A typical 
gas chromatogram for carbon monboxide using such a 
chromatograph is given in Fig. 2. 

5.2.2 Column 

a) Stainless steel, with activated charcoal of 30 to 35 
mesh; 1 00 cm long and 4 to 6 mm in diameter. The 
column is activated at ISO^'C for 3 h; and 

b) Stainless steel, with molecular sieve 5 A (40 to 60) 
mesh: 11 cm long, 4 to 6 mm in diameter, activated 
at 300^C for 3 hours. 

These two columns are in series, with' the charcoal 
column on the injection side. The columns shall be 
activated at regular intervals as the retention time of 
carbon monoxide will decrease. Methane present in 
large concentrations will interfere. 

5.2.3 Conditions 



Carrier gas 


Carrier gas flow 

5 litres/hour 

Sample loop 


Bridge current 

350 mA 

Chart speed 

30 cm/hour 

5.3 Procedure 

Conduct the flow of carrier gas and inject the sample at 
injection port where it is well mixed with carrier gas. 
This is then led into the chromatographic column. The 
constituents of the sample are separated out by virtue 
of their differing interaction with the stationary phase. 
For efficient separation it is necessary that the column 
is maintained at the temperature prescribed in 5,2,3. 
As the sample enters the detector, it gives a signal 
corresponding to the amount of a particular 
constituent, carbon monoxide in this case, leaving the 
column. From the specific area under the peak 
corresponding to carbon monoxide, the quantity of 
carbon monoxide may be determined. 

5.4 Calculation 

Calculate the individual concentrations of the 
constituents on the basis of the peak areas on the 
chromatograph obtained with known amount of 
constituent, namely, carbon monoxide, using the same 
apparatus under identical conditions. 

IS 5182 (Part 10) : 1999 



Fig. 2 Typical Gas Chromatogram for Carbon Monoxide tn Air Sample 

6.1 Principle 

Air containing carbon monoxide is passed over a heated 
catalyst commercially known as Hopcalite and reacts 
to form carbon dioxide. The resultant rise in temperature 
due to exothermic nature of the reaction is a measure of 
carbon monoxide concentration. Glass bead thermistors 
embedded in hopcalite measure the temperature rise. 
Samples containing mg/1 to 500 mg/1 carbon monoxide 
are measured by this method. 


1 The minimum detection limit for this method is ±2 mg/1. 

2 Though the basic instrument is recommended for to 
500 mg/1 range, samples with higher concentration of 
carbon monoxide may be measured by proper dilution. 

6.2 Apparatus 

6.2.1 Gas Monitor 

It shall meet the following specifications: 

a) Monitor should be* suitable for Operation within 
the temperataure range of 15**C to 40X and a 
relative humidity of to 99 percent; 

b) The 95 percent confidence limits of repeatability 
shall be within ±1 ,0 percent fsd. The minimum 

detectable concentration shallbe 2 mg/1 or less; 

c) The maximum deviation between an actual 
instrument reading and the reading predicted 
by a straight line between the upper and 
lower calibration points shall be ±1 percent 

d) Neither the zero drift nor the full scale drift shall 
be greater than ±1 percent fsd in 24 hours, 
excluding changes due to changes of atmospheric 
pressure; and 

e) The response time of the monitor shall be less 
than 5 minutes for 90 percent of the fmal reading 
at a flow rate of 2 litres/min, 

6.2.2 Pump 

Any pump having a flow rate of 10 litres per minute is 

6.2.3 Connecting Tubes 

Tubes of teflon, polyvinyl chloride or polyethylene. 

6.2.4 Arrangement of Apparatus 

The analysing system may be considered as consisting 
of CO monitor and a pump for drawing the air sample 
continuously through the monitor. A needle valve and 
a tlow meter fitted in the monitor control and measure 
the flow of sample air connecting tubes will be required 
between the sampling point, the instrument and the 

IS 5182 (Part 10) : 1999 

pump. Teflon or polyvinyl chloride or polyethylene 
tubes have been found suitable for this purpose. 

6.3 Sample Condii&oning 

6.3.1 Particulate Matter 

Coarse particles present in the gas stream can clog the 
flow meter and needie',valve over a long period of time. 
To overcome these (iifficulties a filter capable of 
removing over 90 percent of 1 fim size particles is fitted 
at the inlet. This filter should be checked at weekly 
intervals when the instrument is continuously used 
and changed if it is clogged or begins to affect the flow 
in the instrument. 

6.3.2 Water Vapour 

Constituents of the air saipple will not interfere if the 
instrument is zeroed wiui carbon monoxide free air 
whose composition is same as the composition of the 
sample to be analysed. 

6.4 Mode of Operation 

The instruments based on catalytic oxidation method 
are used for continuous monitoring of the sample gas. 
For this purpose a flow of 2 litres per minute or as 
specified by manufacturer, is maintained through the 

6.5 Procedure 

6.5.1 Warm-Up Period 

Catalytic oxidation method instruments are operated 
on a continuous basis. However, an initial warm-up 

period of 90 to 100 minutes is required. Air flow is 
maintained during this period -^-^ no measurements 
are made, 

6,5.2 Calculation of Results 

These instruments are direct reading instruments and 
carbon monoxide concentrations may be directly read 
on the meter. 

6.6 Standardization 

6.6.1 Preparation of Standard Gases 

Catalytic oxidation method of gas analysis depends 
on calibration against gas mixtures of known 
composition. Method of preparing reference mixtures 
of standard gases shall be in accordance with the 
relevant Indian Standard. In the absence of these they 
shall be prepared as agreed to between parties 

6.6.2 Calibration Gases 

Two standard gas mixtures are required for calibration 
purposes. One shall contain between 90 to 100 mg/l 
of carbon monoxide in air (span gas) and the 
other air with not more than 1 mg/l carbon monoxide 
(zero gas). 

6.6.3 Analysis of Standard Gases 

The span and zero gases shall be supplied to the 
instrument for calibration at the same temperature, 
humidity and pressure as will obtain when samples are 
to be analysed. 

(Continued from second cover) 

In this revised version, an additional method, namely, catalytic oxidation method which is suitable for continuous 
monitoring, has been incorporated to be used as reference method. 

In reporting the result of a test made in accordance with this standard, if the final value, observed or calculated, 
is to be rounded off, it shall be done in accordance with IS 2:1960 'Rules for rounding off numerical values 

Bureau of Indian Standards 

BIS is a statutory institution established under the Bureau of Indian Standards Act, 1986 to promote 
harmonious development of the activities of standardization, marking and quality certification of goods 
and attending to connected matters in the country. 


BIS has the copyright of all its publications. No part of these publications may be reproduced in any form 
without the prior permission in writing of BIS. This does not preclude the free use, in the course of 
implementing the standard, of necessary details, such as symbols and sizes, type or grade designations. 
Enquiries relating to copyright be addressed to the Director (Publications), BIS. 

Eeview of Indian Standards 

Amendments are issued to standards as the need arises on the basis of comments. Standards are also 
reviewed periodically; a standard along with amendments is reaffirmed when such review indicates that 
no changes are needed; if the review indicates that changes are needed, it is taken up for revision. Users 
of Indian Standards should ascertain that they are in possession of the latest amendments or edition by 
referring to the latest issue of 'BIS Handbook* and * Standards: Monthly Additions'. 

This Indian Standard has been developed from Doc : No. CHD 32 (511). 

Amendments Issued Since Pubilcafion 

Amend No. 

Date of Issue 

Text Affected 



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